Technological development is under way for a disk drive capable of achieving improvements in a data transfer rate and a power-savings by incorporating a semiconductor non-volatile memory (hereinafter, referred to as the non-volatile memory). The non-volatile memory has a high data transfer rate to the disk drive and consumes less power. These developments provide data processing by exploiting the respective characteristics of the disk drive and the non-volatile memory.
A boot program of a computer, such as an operating system, or a frequently used application program may be pre-stored in non-volatile memory, so that start-up time is shortened by increasing the data transfer rate to the host computer. Also, power may be saved by spinning down the disk so that write data is buffered in non-volatile memory or read data is transferred from non-volatile memory during the spin down. The disk drive as described above chiefly uses a flash memory having a low cost per bit, as non-volatile memory. The flash memory has random access capability and consumes little power. However, because the number of overwrites to the flash memory is limited, when flash memory is used by an application in which data is overwritten frequently, flash memory may fail to endure extended use over a long period of time.